Natural At-home treatment for Coryza needed ASAP!

My flock has been infected with Coryza by a recent chick order from a hatchery - I'm loosing chicks about every other day right now.
I have some special circumstances that make treatment difficult - I live in Congo, Africa where I can't go and buy a treatment or seek veterinary care for my animals.

I ordered a batch of special chickens called Kuroilers from the neighboring country of Uganda and had them flown into our village. Two other families went in on the order. My chicks started falling ill three days after I received them two Fridays ago. Symptoms include diarrhea, sneezing, mucus discharge from nose and eyes, limpness, swollen faces and eyes, eye sockets full of puss and blockage, crackling wet noises when affected birds are breathing. My flock of five hens, one rooster, four ducks and a guinea fowl were completely healthy before the introduction of the chicks. I also have turkeys that are separate from the other birds but the runs are connected. One of the other families to purchase chicks along with us has a sick chick. The source is the chicks. They were supposed to come from a good source and be vaccinated - hence I didn't put them in quarantine before putting them in with my flock. (Yes, this was a mistake but please focus on helping me, not lecturing me on proper flock management)

At first I posted on several Facebook groups for help and people thought it was a mixture of things like fowl pox or Cocci. I have tried things in their water and feed to no avail (this was before I diagnosed it as Coryza) - cayenne, garlic, ACV, Oregano EO, Aloe Vera and even am doing a diluted bleach treatment now (when others thought it was Cocci, this has been used effectively). In their feed I have given turmeric, cayenne, cinnamon, garlic, Oregano EO, Rosemary EO, and fed them fresh homemade yogurt mixed with Aloe Vera and Oregano EO.

Nothing is working and my birds are falling ill. Not just the chicks either - one of my broody hens is now showing symptoms. Three of the month-old chicks have died so far and I have another two isolated from the others this morning.

Let me repeat - I do not have access to a vet, antibiotics or other medications of any kind. I have a few Essential Oils, herbs and spices, bleach, Vetericyn, topical triple-antibiotic ointment, and any local plants and produce (think tropical like pineapples, papaya and avocado, etc.).

Is there anything I can give to my flock on a wide basis to help treat and control the spread of this disease? Do you have any suggestions on how to prevent the others who are not showing symptoms from catching the disease?

Wow, this is a challenge... No access to meds... I am very curious on how this will be accomplished, as I mughtvrun across this in the future and I avoid meds at almost every turn, so this information might come in handy...

It also has the distinct sickly-sweet smell near the head like Coryza descriptions. I've been isolating the sick birds, like I mentioned, but now one of my broody hens is sick. She is on a clutch of eggs due to hatch in a week. I'll continue to add aloe to their water to help.

I think your best bet outside of meds is to feed the birds as nutritiously as possible while giving extreme ventilation so their systems can fight the infection.
That may entail vitamins, amino acids and some trace elements. Do you have access to seaweed or kelp?
What kinds of fruits/berries do you have ripening now?

No seaweed or kelp of any kind. We don't have berries here but there are tropical fruits like pineapple, mangos, passion fruit and guava. I'm giving them free-choice garlic and yogurt mixed with aloe. I can mix some molasses into their water along with the aloe and garlic.